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Macro-and microscopic mechanical behaviour of flow of coal samples experimentally deformed at high temperatures and pressures

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Chinese Science Bulletin 2005年第S1期50卷 59-66页

作者： LIU Junlai , YANG Guang & MA Rui State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Beijing 100083, China Key Laboratory of Lithosphere Tectonics and Lithoprobing Technology of Ministry of Education, China University of Geosciences, Beijing 100083, China College of Earth Sciences, Jilin University, Changchun 130061, China State Key Laboratory of Geological Processes and Mineral Resources China University of Geosciences Beijing China Key Laboratory of Lithosphere Tectonics and Lithoprobing Technology of Ministry of Education China University of Geosciences Beijing China College of Earth Sciences Jilin University Changchun China

Coal samples from Qinshui Basin, Shanxi, China are experimentally deformed at temperatures and confining pressures of 200 - 500℃and 200 - 500 Mpa, strain rate of 0.5×10-5/s and total strain of 10%. The vitrinite reflectance of the coal samples varies from 3.04 to 1.79. It is shown that the strengths of the deformed samples change obviously with coeval increasing temperatures and pressures (T/P). At the experimental range of T/P, the effects of increasing temperature predominate over that of increasing pressure. Microstructural analysis indicates a brittle to ductile transition under experimental T/P conditions from 200 to 300℃, and 200 to 300Mpa. brittle deformation microstruc-tures include macroscopic fracture zones and penetrative fracture associations. Elongation, undulose or irregular extinction, deformation lamellae and dynamic recrystallization of grains are the main ductile deformation microstructures. The variation of deformation mechanisms of the experimentally deformed coal samples is related to both the components of coals and T/P conditions. At low T/P, fractures occur in both inertinite and vitrinite of the samples. At higher T/P, crystalline plastic deformations are observed in the inertinite only.

关键词： coal experimental deformation brittle to ductile transition.

THE BEHAVIOUR OF1/2[112] SUPERLATTICE DISLOCATIONSIN POLYSY NTHETICALLY TWINNED CRYSTALS OF TiAl

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中国有色金属学会会刊：英文版 1999年第S1期9卷 81-86页

作者： Yi Liu 1,2 , Dongliang Lin (T. L. Lin) 1, Shipu Chen 1, Zhongguang Wang 2 and Zhiguo Liu 3 1 Department of Materials Science, Shanghai Jiao Tong University, Shanghai 200030, China 2 State Key Laboratory for Fatigue and Fracture of Material

The behaviour of 1/2〈112] superlattice dislocations in polysynthetically twinned (PST) crystals of TiAl at elevated temperatures have been investigated by transmission electron microscopy (TEM). The results showed that 1/2〈112] superlattice dislocations play an important part in the deformation. At room temperature, 1/2〈112] superlattice dislocations can be activated easily but are often dissociated into partials trailed by faulted dipoles with super extrinsic stacking faults (SESFs) and difficult to move. In situ heating observations on the faulted dipoles showed that annihilation of the partials bounding the SESFs of the faulted dipoles occurred and resulted in discontinuous stacking faults along the direction of the partials at about 500 ℃. The faulted dipoles disappeared completely at about 600 ℃. The temperature range of annihilation coincided with that of brittle to ductile transition of TiAl PST crystals reported by Inui et al (1995). At 850 ℃, they are often dissociated into partials including super intrinsic stacking faults (SISFs) and can move easily. The experimental observations suggest that the behaviors of 1/2〈112] superlattice dislocations control the phenomenon of brittle to ductile transition of PST crystals of TiAl alloy.

关键词： PST crystals TiAl superlattice dislocations dissociation brittle to ductile transition

DUCTILEbrittleTRANSITION OF POLYCRYSTALLINE Ni_3Al WITH VARYING GRAIN SIZE

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中国有色金属学会会刊：英文版 1999年第S1期9卷 125-129页

作者： G. W. Han, D. Feng and C. S. Lee  Central Iron & Steel Research Institute, Beijing 100081, China  Dept. Physical & Mater. Sci., City University of Hong Kong Hong Kong, China

It is known that in B (un)doped Ni 3Al polycrystals, the dependence of yield strength on grain size follows the Hall Petch relationship: σ y= σ 0+ K y d -1/2 , and the slope K y can be reduced by B doping owing to the lowering of grain boundary resistance to slip transmission. If the intergranular cracking in polycrystalline Ni 3Al occurs from the microcavity along the grain boundaries, the effective external tensile stress for the propagation of the crack like microcavity along the grain boundaries can be deduced as: σ f= σ i+ K u d -1/2 , where K u reflects the effects of such factors as environment, strain rate, boron doping and the orientation of the grain boundary on the trend of intergranular cracking. For loaded polycrystalline Ni 3Al, it should be competitive between the intergranular cracking and slip transmission across the grain boundary. Therefore, comparing the varieties of both σ y and σ f with grain size, the dependence of ductile brittle transition on grain size, and the effects of the above factors on ductile brittle transition can be expected. The model also predicts that there exists a critical grain size for the ductile brittle transition of polycrystalline Ni 3Al alloys, and B doping can increase the critical grain size due to the reduction of the slope K y and the increase of K u. The reported experimental results verified the above model.

关键词： Ni 3Al grain size ductile brittle transition Hall Petch relationship

NONEQUILIBRIUM STATISTICAL THEORY OF FATIGUE FRACTURE (Ⅱ)——FROM MICROSCOPIC MECHANISM TO MACROSCOPIC PROPERTIES OF FATIGUE FRACTURE

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中国科学A辑(英文版) 1986年第12期29卷 1318-1333页

作者：邢修三 Institute of Atomic Energy Beijing

The stochastic evolution equation of microcracks is given. The microcrack density distribution function is obtained on the basis of dislocation mechanism. The fatigue fracture probability, reliability, σ_a-N curves,... 详细信息

关键词： fatigue deviation stochastic Probability dislocation quantities latter brittle hardening infinite

Emplacement and Evolution History of Pegmatites and Hydrothermal Deposits, Matale District, Sri Lanka

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International Journal of Geosciences 2011年第3期2卷 348-362页

作者： G.W.A.R Fernando A Pitawala T.H.N.G Amaraweera 不详

Excellent outcrops in Matale Sri Lanka provide unique insight into the emplacement and evolution history of hydrothermal and pegmatitic rocks in the central highlands of Sri Lanka. Field, structural, petrological, thermo-barometric studies in the metamorphic basement rocks in the central highlands and related hydrothermal deposits are presented in this study. Detailed petrographic and mineralogical data reveal peak metamorphic conditions for the crustal unit in the study area as 854 ± 44oC at 10.83 ± 0.86 kbar. Hydrothermal veins consisting of quartz and mica are closely related to cross-cutting pegmatites, which significantly post-date the peak metamorphic conditions of the crustal unit. Field relations indicate that the veins originated as ductile-brittle fractures have subsequently sealed by pegmatites and hydrothermal crystallization. Geological, textural and mineralogical data suggest that most enriched hydrothermal veins have evolved from a fractionated granitic melt progressively enriched in H2O, F, etc. Quartz, K-feldspar, mica, tourmaline, fluorite and topaz bear evidence of multistage crystallization that alternated with episodes of resorption. It was suggested that the level of emplacement of pegmatites of the Matale District was middle crust, near the crustal scale brittle-ductile transition zone at a temperature of about 600oC. For this crustal level and temperature range, it is considered very unlikely that intruding pegmatitic melts followed pre-existing cracks. As such the emplacement temperatures of the pegmatites could be well below the peak metamorphic estimates in the mafic granulites. The metamorphic P-T strategy and position of formation of hydrothermal deposits and pegmatites is summarized in the modified P-T-t-D diagrams.

关键词： Hydrothermal veins Pegmatites Emplacement history brittle deformation Sri Lanka

Deformation Mechanisms of Carrara Marble Under Increasing Temperatures from 300℃ to 550℃

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Global Geology 2000年第2期5卷 161-168页

作者： Ma Lijie Liu Junlai Li Haifeng Wang Xiaoyong Zhong Xinyong Dept. Earth Sci. Jilin University Changchun 130061 P. R. China

Deformation experiments of Carrara marble were conducted under increasing temperatures (temperatures 300℃ - 550℃, confining pressure 0. 5Mpa, strain - rate 5 × 10- 6 s-1 ). The experiments reveal that calcite rocks show different deformation behaviors and corresponding microstructural characteristics under different temperatures. By analyzing microstructural characteristics, preferred grain shape orientation variation of the primary rocks and deformed specimen, the deformation features of Carrara marble are summarized: twinning, fracturing dominates deformation of the rocks at temperatures between 300℃ and 450℃; dynamic recrystallization occurs in the temperature range of 450- 550℃; the brittle to crystalline plasticity transition deformation is observed at around 450℃, twinning and crystal - plastic deformation become dominant with further increasing temperature.

关键词： Carrara marble Experimental deformation Deformation mechanisms brittle - plastic transition

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SEISMIC GEOLOGY

Abstracts of Chinese Geological Literature 2009年第3期25卷 15-22页

20091465 Cai Xuelin(College of Earth Sciences,Chengdu University of Technology,Chengdu 610059,China);Cao Jiamin Preliminary Study on the 3-D Crust Structure for the Longmen Lithosphere and the Genesis of the Huge Wenchuan Earthquake,Sichuan Province,China(Journal of Chengdu University of Technology,ISSN1671-9727,CN51-1634/N,35(4),2008,p.357-365,8 illus.,39 refs.)Key words:deep-seated structures,large earthquakes,Longmenshan Fracture ZoneBased on a structural analysis of many seismic sounding profiles,there are two fault systems in Longmen collisional orogenic belt,Sichuan Province,China.They are both different obviously and correlative closely.One is shallow fault system composed mainly of brittle shear zones in surface crust,and the other is deep fault system composed mainly of crust-mantle ductile shear zones cutting Moho discontinuity.Based on the result of researching geological structure and seismic sounding profiles,

关键词： crust mantle shallow sounding Chengdu brittle orog

Relationship between Fracture Toughness and Fracture Surface Fractal Dimension in AISI 4340 Steel

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Materials Sciences and Applications 2013年第4期4卷 258-267页

作者： Luis R. Carney John J. Mecholsky NAVAIR Jacksonville Jacksonville USA Materials Science & Engineering Department University of Florida Gainesville USA

This study analyzes the relationship between fracture toughness and the fracture surface fractal dimension for a set of twenty-four CT-type AISI 4340 steel specimens heat treated to a variety of tensile strengths. Specimens were tested in accordance with ASTM E 399. Their respective fracture surfaces were plated, polished, photographed under an SEM in BSE mode and measured according to the Richardson method to obtain fractal dimensions. For brittle materials the limited results are consistent with previous literature: increasing fractal dimension with increasing toughness. For partially or fully ductile materials the results indicate a decrease in fractal dimension with an increase in fracture toughness. The data are modeled using a variation of the function applied to ceramics. Fracture in a ductile mode is characterized by the formation of dimples which exhibit fractal characteristics. The results are discussed in terms of the micromechanisms of fracture.

关键词： Fractal Fracture Ductile Failure brittle Failure Mechanical Behavior

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GEOPHYSICS

Abstracts of Chinese Geological Literature 2004年第1期20卷 11-15页

20040059 An Yulin (School of Geophysics and Information Technology, China University of Geosciences, Beijing); Chen Yudong Advance in Theory and Method for Forward and Inverse Problem of Gravity and Magnetic Prospecting (Earth Science Frontiers, ISSN1005-2321, CN11-3370/P, 10(1), 2003, p. 141-149, 2 illus. , 40 refs. , with English abstract)

关键词： Forward brittle strike tables Continental electr GEOPHYSICS mantle Tibet magnetization